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By Corby G. Anderson

Over the past 15 years, numerous pressure oxidation plants for pretreatment of gold ores and concentrates have been installed throughout the world. While this technology is now established, it suffers in terms of the complex engineering and operational characteristics inherent in utilization of high temperatures (i.e. up to 225oC) and high pressures (i.e. > 3000 kPag). This paper outlines the application of an industrially proven pressure leaching methodology utilizing nitrogen species catalyzed pressure leaching and alkaline sulfide gold leaching. As such, it stands as an economic and engineering advancement in pressure leaching and non-cyanide treatment of gold ores and concentrates. In particular, the technology offers significant technical and economic advantages over traditional pressure oxidation and cyanide gold recovery in the treatment of gold bearing chalcopyrite ores and concentrates. An example of this will application will be delineated in this paper.

Jan 1, 2003

By Jae-Chun Lee, Jinki Jeong, Manis Kumar Jha, Divika Gupta, Pankaj Kumar Choubey

Rare metal indium (In) is mostly used as electroluminescent material in liquid crystal displays (LCD) monitors. Present paper describes leaching studies for the recovery of In from waste LCD monitors in presence of different other impurities. The leaching studies showed that more than 85% of In was leached out using 20% sulfuric acid at 60oC in mixing time 30 min at fixed pulp density 25 g/L. The solution could be purified using SX/IX and from the pure solution metal/ salt could be produced by evaporation, precipitation, electrolysis, crystallization processes.

Jan 1, 2014

By Ilona Johnson

United States metals and non-metallic minerals manufacturing consume about 5,000 trillion Btu annually. Various studies estimate that as much as 20 to 50 percent of this energy is lost as excess or waste heat. Recovery of waste heat can conserve energy, reduce operating costs, and lower environmental emissions. It would be valuable to quantify recoverable waste heat sources and identify the barriers that hinder its recovery. This paper provides an overview of waste heat losses specific to high temperature processes in primary metals and minerals manufacturing. It summarizes findings from a broader study conducted for the Department of Energy Industrial Technologies Program; the study evaluates energy losses, recovery practices and opportunities, and R & D needs for waste heat technology development.

Jan 1, 2008

By Dao Su, Ganghua Fu, Xuling Chen, Yufeng Guo, Min Gan, Tao Jiang, Xiaohui Fan

"The sinter quantity and quality of limonite in the magnetite and hematite sintering models were studied and compared. For the sintering of magnetite, the results showed that the increase of limonite improved the permeability of sinter mixture, increased the sinter quantity and quality. The sinter strength and productivity were decreased when the proportion of limonite exceeded 50%. The appropriate proportion of limonite was 40%-50%. For the sintering of hematite, the sinter quantity and quality were first maintained at the same level thereafter declined, more obviously when the proportion of limonite exceeded 40%. The amount of calcium ferrite increased whose shape changed from acicular to leaflike and block gradually with the proportion of limonite increased from 0% to 80%.IntroductionWith the fierce competition of domestic and overseas iron markets in the twenty-first century, cheap ores such as limonite are used to be sintering raw materials to cut the costs of sinter and pig iron for steel making, and boosts the competitiveness of steel companies [1, 2]. In addition, as the reserve volume of hematite of high grade is reducing year by year, the usage amount of limonite in sintering are expanding in major domestic and international sintering plant [3, 4]. Sintering can be divided into two types, majoring in concentrates and fine ores, according to the different types of raw materials. The sintering characteristics of limonite in the two types above have been studied and compared in this paper, which makes a significant sense for the research of limonite sintering properties and guidance of ore proportioning in sintering plants."

Jan 1, 2012

By Antti Roine

Sulfidic zinc concentrates are usually roasted in a fluidized bed furnace into sulfur-free oxide form. Metallic zinc is produced from this oxidic calcine using hydrometallurgical leaching, solution purification and electrowinning stages. The roasting step is necessary because zinc oxides are easier to dissolve using traditional leaching methods than zinc sulfides. The Kokkola Zinc smelter uses various types of zinc concentrates and secondary materials as feed mixture. This makes it difficult to find optimum process parameters for the roaster when the composition and particle size distribution of the feed mixture varies even on a daily basis. Certain conditions may even cause difficult accretion problems or increase the amount of calcine in the process off-gas line excessively. A thermochemical heat and material balance model was developed for process advisor, in order to estimate the effects of different process parameters (temperature, process air coefficient, concentrate feed, oxygen enrichment, water feed, etc.) on the heat balance, roasting temperature and calcine composition. This model was constructed using the heat balance module of HSC Chemistry 4.0 software. The prevailing chemical compounds in the concentrate and calcine were verified using mineralogical analyses and equilibrium calculations. The roasting process seems to operate near chemical equilibrium conditions, if the behavior of the main components is considered. This paper describes briefly the basic principles of the calculation model and outlines the results with several diagrams and discussion. The calculated results were in reasonable agreement with the recent process air oxygen enrichment and water feed test campaigns carried out at Kokkola in 1999.

Jan 1, 2000

By Sergey Shabala

Green leaf tissues convert solar energy into the energy of chemical bonds of sugar molecules during the process of photosynthesis. The efficiency of this conversion can be much higher than efficiency of any of the currently known silicon-based solar panels. Importantly, vast amounts of CO2 are assimilated during this process. The efficiency of photosynthesis is critically dependent on the availability of a large number of nutrients, among which metal cations such as K, Ca, Mg, Cu, Zn, Fe, Mn, and Ni play a key role. In this paper I summarize basic requirements and major functions for each of these essential nutrients in plant photosynthesis, both at the whole-plant and molecular level. I will talk about how these requirements may be affected by the global climate trends and discuss the prospects of creating artificial photosynthetic “bioreactors” for efficient energy conversion and CO2 assimilation.

Jan 1, 2009

By F. Begazo

The most common approach to increase production in copper refineries is to increase current densities. However, if these increases are not well thought out beforehand and are not properly and effectively controlled, the end results could be reduced plant performance and a deterioration in cathode quality. Both of these factors result in lower efficiencies and increased costs. At the Ilo Refinery of Southern Peru Copper Corporation, a modernization and expansion program was implemented shortly after the Refinery was purchased from Minero Peru, in 1994. This program was intended to increase production from 195,200 mtpy of cathode to 227,000 mtpy over a 3-year period. Part of this production increase would come from increasing current density. During the period from 1994 to 1997, current density at the Ilo Refinery was increased from 218 A/m2 to 230 A/m2, while plant efficiencies were maintained at consistently high levels. The current efficiencies were maintained at >97.5% and time efficiencies were maintained at >98%. During 1998, additional increases in current density were implemented while the high plant performance was maintained at the same levels. By the end of 1998, the current density was 241 A/m2, while current efficiency and time efficiency of 98% were maintained. This paper describes the control processes used at the Ilo Refinery to maintain high plant performance levels while increasing the current density. Additionally, expected plant performances from extended test programs at current densities up to 280 A/m2, for future production increases, are reviewed and discussed.

Jan 1, 1999

By John R. Goode

Barrick Gold Corporation operates gold mines in the United States, Chile, 'Peru, Canada, and in the near future, in l1anzania. Barrick meets environmental requirements and limits the potentially adverse effect of cyanide discharge to the environment using various cyanide destruction techniques. Barrick operations use, or have used, natural degradation, ferrous sulphate, hydrogen peroxide, Caro's acid, alkaline chlorination, and the SO/Air process for cyanide destruction. This paper presents a general discussion of the options for controlling cyanide in plant effluent and provides details of Barrick's operating experience including general notes on costs.

Jan 1, 1998

By Yoichi Takeda

Copper solubility in Si02-CaO-FeOx slag equilibrated with copper matte in 10% S02 atmosphere at 1573K was estimated. Essential parameters are activity coefficients of copper oxide and sulfide, oxygen and sulfur potentials and activity of copper in the slag-matte system. A large number of experiments provide proper parameters to calculate copper solubility in slag. A classical thermodynamic model postulating CUOO.5 and CuSo.; molecules assists in estimating copper solubility in slag. Additions of Si02 and CaO reduce copper solubility almost in any condition. Copper loss, that is function copper solubility and slag volume, in the silica saturated Si02-FeOx binary slag is minimally equilibrated with less than 66% copper matte while copper loss in the 50% FeOx-SiOrCaO ternary slag saturated with 2CaOSi02 is minimally equilibrated with over 66% copper matte. This slag composition has potential for continuous copper converting, direct copper production or high-grade matte production.

Jan 1, 2003

By Qin Hua, Xiangru Chen, Qijie Zhai, Yongsheng Yan, Liang Chang

"In this paper, pure bainite ductile iron and their alloying form of 0.2wt% niobium were prepared by a controlled cooling heat-treatment. The effect of niobium alloying on the microstructure, hardness and impact toughness of bainite ductile iron was studied. The results show that adding niobium effectively improves the hardness and toughness of bainite ductile iron. The hardness and the impact toughness of niobium-alloyed bainite ductile iron were investigated by varying the temperature at which samples were fed to the incubator.IntroductionThere are two essential methods to prepare the bainite ductile iron: isothermal quenching [I-31, and alloying [4• 51• Isothermal quenching process is very time and energy consumable, concerned as a high cost technique for mass production. Besides, there are certain limitations on the size and shape of castings in this process. In addition, it potentially harms the environment. As for the alloying, Ni, Mo, and Cu have to be utilized to obtain bainite. However, the large demand and high cost of Ni makes it not feasible in practice.It is well known that niobium can promote the formation of carbon compound, and improves the stability ofundercooled austenite, which is preferred to the increase of the hardenability. Previous studies showed that niobium could refine the grain and improve the mechanical properties of gray cast iron [6-81 • Therefore, in the present work, the effects of niobium and the temperature at which samples were fed to the incubator on the microstructures and properties of niobium alloyed bainite ductile iron were investigated."

Jan 1, 2014

By R. N. Reddy

The Pseudo capacitance of layered type Mn02 electrode material for electrochemical capacitors (EC's) was investigated. MnO2 was synthesized in our laboratory. Mn02 was prepared from heating of KMn04 at 300°C in air. Cyclic Voltammetry (CV) experiments were carried out using three electrode system, Saturated calomel electrode as reference electrode, platinum mesh as a counter electrode, and MnOz composite material mounted in a platinum mesh used as a working electrode. Two kinds of composite working electrode materials were used, one was mixture of MnOz and 25 wt% acetylene black, while the other was MnOz, 25 wt% acetylene black and 25 wt% carbon. All the experiments were carried out at 25OC. A maximum specific capacitance of 130 Fig and 118 Fig were observed at the scan rate of 2 mV/s and 20 mV/s respectively in 1M KC1 for composite electrode made with carbon. Results obtained in this study are compared with that of other electrode materials.

Jan 1, 2002

By Jinfu Xu, Youqing Cao, Yuting Lv, Hang You, Peng Jiang

"In present work, we reported the fabrication of composites consisted of M42 powder metallurgy high speed steel and 45 steel at one step via spark plasma sintering (SPS) technology. The interface microstructure, compositions and microhardness with the interface forming mechanism were investigated. The results show that the morphology and microhardness within the M42/45 steel interfaces exhibit a gradient distribution. The interfaces possessed a transition layer up to 10.2 ?m with few distortions and microcracks. The formation of M42/45 steel interfaces were driven by both fusion and diffusion processes. The former one was primary at the early sintering process, while the later one becomes dominant over the followed sintering process.IntroductionPowder high-speed steels have been widely used in cutting tools, cold-hot tools and dies, as well as in cut materials and structure parts with wear resistance and high-temperature resistance, due to its high hardness, good wear resistance, desirable cutting toughness and favorable hot hardness [1-2]. For materials of some parts in practical production, not only the favorable toughness is required to resist the impact action, but also the high hardness and exceptional wear resistance are demanded. According to the functional requirements and working conditions, bimetal composite materials are prepared in a certain mode, proportion and distribution, by designing two metals with different chemical and physical properties [3-6]. Considering the composites exhibit different properties in different positions of the parts with a combination of the advantages of two metals, they can obtain enhanced properties that the single one can not achieve."

Jan 1, 2012

By Xiaobing Yang, Abhishek Lahiri, Animesh Jha

"In the FFC-Cambridge process, the cathodic dissociation of oxide and CO/CO2 production on carbon anode is the basis for metal production in a CaCl2 bath. By using an inert intermetallic anode, the CO2 evolution can be eliminated altogether with acceleration in the electro-reduction kinetics. At present the process suffers from slow reduction kinetics of TiO2 to Ti metal, which can be enhanced significantly by the incorporation of alkali species in the TiO2 pellet at the cathode and in the CaCl2 bath in the presence of an intermetallic inert anode. Nearly full metallization with greater than 99% of Ti metal containing 1500 ppm of oxygen is possible to achieve in less than 16 hours of electro-reduction. Analyses of phase composition and the microstructures morphology in fully metallized pellets revealed the presence of localized solidified Ti layer, indicating that fast reduction process also involved formation of liquid phase as middle stage reaction. In addition, in situ creation of porosity and maintain higher current level during electrolysis process were two key factors to fully reduction of TiO2.IntroductionDuring cathodic dissociation of TiO2 in a CaCl2 bath and anodic evolution of CO2 on a carbon anode, which is the basis for the FFC Cambridge process [1], the rate of metallization slows down due to the formation of CaTiO3 at the reaction interface. Calcium and alkaline earth perovskites are known for their poor electrical conductivity which adversely affects the overall electro-reduction. One of the ways to increase the porosity is via the addition of polyethylene precursors in the pellet or by directly starting from perovskite [2, 3]. The experimental evidences shown in the literature confirm although the speed of reaction increases, but a complete or near complete metallization is not possible by enhancing the in-situ porosity alone, as the insulating perovskite is very slow to decompose under the equilibrium that prevails in the cell. Plethoric evidences on carbon anode show with the current decrease gradually, and finally stabilize at a very low value between 0.2 and 0.4 A, which is a testimony of the presence of perovskite insulating barrier in the current path. Our aim in this paper is to demonstrate the mechanism of enhanced electro-reduction when alkali ions are present in the oxide pellet at cathode and in the bath. We also show for the first time the use of an intermetallic anode for Ti-metal production using the FFC Cambridge process."

Jan 1, 2009

By Francis Vanbellen

In Union Minière's Hoboken smelter and refinery for complex non-ferrous materials, the treatment of recycling products, containing precious metals, occupies a dominant place. For all feed materials, the first step, prior to their treatment, is to classify them in order toselect an accurate and economical procedure for sampling as well as to dispatch them to the optimal process scheme. More than 150 different procedures for sampling are commonly used. The most important ones are briefly discussed in the paper. Precious metals bearing recycling materials vary widely with respect to their physical aspect, their chemical composition and the value of their precious metal content. All these parameters are taken into consideration to select the most appropriate process among the multiple possibilities of Union Minière's flexible integrated flow-sheet. Different stages of the operations as well as the main flow-sheets are described.

Jan 1, 1995

By Eun Duck Park

The gold catalyst supported on iron oxide was prepared from gold dissolved in aqua regia by a deposition-precipitation method and applied to CO oxidation in the absence and presence of hydrogen. Some characterization methods such as X-ray diffraction (XRD), nitrogen adsorption, transmission electron microscopy (TEM), temperature programmed reduction (TPR), temperature programmed oxidation (TPO), and the pulsed CO chemisorption with temperature programmed desorption (TPD) were conducted to explain different catalytic activities of Au/Fe2O3 catalyst pretreated at different conditions. The particle size of gold was about 10 nm for Au/Fe2O3 calcined in air at 373 and 573 K. For complete CO oxidation, the decreasing CO conversion with a reaction time was observed at low temperatures but its initial catalytic activity can be restored by a heat treatment at high temperatures. This catalyst was quite active for the selective CO oxidation in the presence of hydrogen especially at low temperatures. In the presence of hydrogen, the deactivation was significantly diminished.

Jan 1, 2006

By Yang Hong-ying, Yu Juan

Electrochemical behavior of natural chalcopyrite in electrolyte solution at pH value of 6.97 was studied by cyclic voltammetry, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. The results showed that the electrochemical processes occurred on electrode surface were controlled mainly by the growth of sulfur species at lower applied potentials (<0.35Vvs.SHE), and the oxidative dissolution of sulfur species and the hydroxylation of iron at higher applied potential (>0.45V). The EIS spectra of oxide product layers could be illustrated by the equivalent circuit of Re(QdlRct(QfRf)), and the degree of hydrophilicity for chalcopyrite was higher when the value of charge transfer resistance Rct. was greater. The optimum potential range for the floatation of chalcopyrite in collectorless solution at pH value of 6.97 was between OCP (0.165V) and 0.35V.`

Jan 1, 2015

By Bowen Li, Matthew D. Andriese, Jiann-Yang Hwang, Zhiwei Peng

"Magnetic iron sulfide ore particles heat rapidly by microwave (MW) irradiation generating plasma during oxidation of surfaces. The high temperatures produced by the exothermic event decompose local portions of samples forming a differentiated flux of partially melted silicate (si-mt) with entrained metal-sulfide (sul-mt) droplets. The si-mt forms crystals of olivine (01) in Ca-rich pyroxene (Cpx) melt that resorbs a portion of iron sulfide (Po). The immiscible sul-mt droplets of (Fe,Ni,Cu)1-xS contain magnetic subsolidus Ni-pyrrhotite (Ni-Po) with Cr-bearing ferrospinel (Mag). Sub-micron sized flecks of Au are found on the surface of a sul-mt droplet with scanning electron microscope (SEM).IntroductionSulfide ore deposits supply the world's mineral resource in the production of non-ferrous metals. Particularly, Cu-Ni deposits are chemically enriched in metals from high sulfur saturation during magmatic formation that creates the proper geochemical environment for metals enrichment [1, 2]. The sulfur and oxygen fugacity control redox conditions of a differentiated silicate/sulfur magmatic melt with the concentration of iron playing a dominate role in the chemical partitioning of metals in sulfide liquid [3, 4]. The initial magnetic crystallization of (Fe,Ni)i-xS monosulfide solution (mss) from metal-sulfide liquid has an exclusive effect on the fractionation of mineral assemblages (zoning) [5].Phase equilibria of sulfide melt (sul-mt) components are related by a miscibility gap with mss forming Ni-rich pyrrhotite (Ni-Po) followed by the crystallization of (Fe,Cu)1-xS intermediate sulfide solution (iss) [6]. Precious metals form stable chacogenides and are retained in solution until the final liquid solidifies. The redistribution of metals now occurs by subsolidus cooling of mss and iss that exsolve low-temperature Fe-Cu-Ni bearing mineral assemblages [7]. The proper interpretation of ore genesis increases processing capabilities by isolating chemically enriched zones during extraction and should be used to aid in sustainable mine site development [8-11]."

Jan 1, 2013

By Louis J. Mittoni

"It is well known that gas injection systems can exhibit a wide range of dynamical behaviours, ranging from linear periodic bubbling through to highly complex turbulent jetting. Recently, it has been observed that an important intermediate regime exists under certain system conditions, where the dynamics are complex in nature yet predictable for short time periods. This paper reviews the evidence to support the above hypothesis, and discusses the invariant quantitative measures such as density, return maps, Lyapunov exponent and dimension which may be used as pattern recognition features in a mOnitoring and control strategy.INTRODUCTIONThere has been a great deal of research on the submerged injection of gases into liquids. This interest is primarily due to the large number of applications in the pyrometallurgical and chemical engineering industries. Gases are typically injected into liquids to achieve goals such as heat and mass transfer, or physical mixing and agitation. Only recently though has the possibility of using the evolution of the gas dynamics as a probe to internal system conditions been raised [1, 2].At very low gas injection rates and small upstream chamber volumes, gas normally disperses in the form of stable bubbles of constant volume [3]. With increases in gas flow rate, the dynamics become more complex, bifurcating into double bubbling, multiple bubbling and complex coalescence behaviour. Irregularities measured in pressuretime series acquired upstream of the injection port under these complex conditions have usually been treated as bothersome noise or contamination to be filtered from the signal and ignored in the analysis. These irregularities, however, may contain physically interesting and useful information on the system from which they were produced if the system may be classified as deterministically chaotic [4]."

Jan 1, 1996

By Bohumír Cech, Jirí Hanika, Václav Veselý

"PET bottles are separated and subsequently crushed into flakes. Except for PET, these flakes contain PE, PVC, paper, adhesives, beverages remainders and mineral impurities. PET itself usually is a glycol and terephthalic and isophthalic acid polymer.The suggested method consists in PET flakes crystallization at 255°C. In the meantime, volatile substances evaporate and PVC disintegrates. Formed crystalline PET is crushed into small particles and then is subject to the basic hydrolysis at an atmospheric pressure. In addition to lye solution, glycol is added in the hydrolysis. Water is eliminated by boiling, which gives rise to suspension of sodium salt of terephthalic acid and glycol. The suspension is skimmed and the filtered glycol is vacuum distilled. Pure glycol is then the distillation product.Crystals are dissolved in water and the solution is filtered, which eliminates PE and impurities. Electrodialysis removes pure terephthalic acid salt from the solution. Glycol solution is returned to the hydrolysis. Terephthalic acid is precipitated by a mineral acid. Subsequently, it is washed and dried. The filtrate is separated through electrodialysis to lye and acid. The lye gets back to the hydrolysis and the acid is used for precipitation. Terephthalic acid and glycol are products in a “polymer grade” quality. The waste is a part of washing waters, distillation residues after glycol regeneration and a filter cake after the terephthalate solution filtration."

Jan 1, 2008

By Preben Ingerslev

Control of the reheating of ingots is based either on surface temperature measurements using optical pyrometers or on furnace set points and reheat time determined empirically. This paper presents a real-time mathematical heat flow model, named BESTT, which calculates the temperature distribution in an ingot cross section when reheated or cooled. The model runs on a 486 PC in less than one minute for a variety of ingot cross sectional shapes such as circular, square and with some considerations octagonal and heavy-cornered square. Initial temperatures can either be uniform or nonuniform while accounting for temperature dependent thermophysical properties. The model was developed and verified using 718 alloy ingots in box type furnaces. When integrated with on-line pyrometric measurements, BESTT can provide for improved feed back in the reheating control loop. The use of BESlT will assist in reducing energy costs, and improving product quality and consistency. EPD Congress 1994 Edited by C. Warren The Minerals, Metals k Materials Sodety, 1993

Jan 1, 1994